Isolation of caliciviruses from skunks that are antigenically and genotypically related to San Miguel sea lion virus

Abstract

Caliciviruses were isolated from feces of skunks imported from the north central United States to Canada. Virus isolation was accomplished using adenovirus-transformed human kidney (293) cells, swine testes and Vero cells. Plaque size variants were present, but there was no apparent difference in virus morphology by negative stain or immune electron microscopy. Pigs infected with skunk calicivirus had a slightly elevated body temperature at 3 days postinfection. Although the infected animals seroconverted, no overt clinical signs were observed. Purified infectious genomic skunk calicivirus RNA behaved exactly as San Miguel sea lion virus (SMSV) 1 and 4 genomic RNA in cell culture transfection studies. Of the cell types examined, only primary porcine kidney, 293 and Vero cells supported viral replication. No viral replication was detected in cells of bovine, equine, ovine, caprine or feline origin. The skunk caliciviruses contained a single capsid protein with a relative mobility similar to SMSV virus 1 and 4 capsid proteins. The capsid protein was positive by Western blot analysis with SMSV and vesicular exanthema of swine virus (VESV) antisera. Purified RNA from skunk calicivirus infected cells was subjected to reverse transcription followed by polymerase chain reaction. Nucleotide sequences were identified that had greater than 85% similarity to the 2C and RNA polymerase gene regions of SMSV 1 and 4 and VESV A48. Predicted amino acid sequences of these regions were greater than 95% similar and the partial coding sequence of the polymerase gene contained the YGDD sequence common to positive-strand RNA virus polymerases.